Effects of Corrosion Aggressiveness on MSE Wall Stability in Nevada

Abstract

Nevada Department of Transportation has over 150 mechanically stabilized earth (MSE) retaining walls at 39 locations. Recently, high levels of corrosion were observed due to accidental discovery at two of these locations. The resulting investigations of these walls produced direct measurements regarding the metal losses of the soil reinforcements and electrochemical properties of the MSE reinforced fill. One MSE wall (I-515/Flamingo) was replaced with a cast-in-place concrete tie-back wall at great expense because of the significant metal loss due to corrosion. There are two other walls at this intersection that were not mitigated. It is now known that aggressive reinforced fill has been used in a number of MSE walls in Nevada. In its characterization of MSE reinforced fill the Nevada Department of Transportation has used the Nevada T235B soil resistivity test method. The Nevada test method under-predicts the corrosive nature of reinforced fill soils when compared to the AASHTO T-288 test method. As the MSE wall investigations show, this under-prediction has proved detrimental to the service lives of MSE structures. The internal stability analyses (using AASHTO 2007 LRFD) of two remaining MSE walls at one intersection were performed using metal loss models developed from the statistical analysis of the direct measurements of metal loss. The results of an investigation that incorporates a statistical analysis in order to effectively undertake a prediction of the internal stability of the two remaining walls due to metal loss is presented in the paper. Other MSE walls in Nevada may also be experiencing similar high rates of corrosion which will result in a deteriorated internal stability.